1. Field of the Invention
The present invention relates to a method of sealing an electric wire-connecting portion formed by connecting together conductive ends of a plurality of electric wires, in which electric insulation and waterproofing property of the electric wire-connecting portion are secured by covering the electric wire-connecting portion. Furthermore, the present invention also relates to a tool for holding a heat shrinkable tube used in the sealing method, and a tube shrinking machine for heating a heat shrinkable tube covering the electric wire-connecting portion.
The present application is based on Japanese Patent Application No. Hei. 9-342971, which is incorporated herein by reference.
2. Description of the Related Art
An example of a method of protecting an electric wire-connecting portion in which conductive ends of electric wires are bundled and connected to each other, will be described with reference to FIGS. 9 through 11.
In FIG. 9, conductive ends of a plurality of electric wires W are bundled and connected together to form an electric wire-connecting portion 1. The electric wire-connecting portion 1 is subjected to thermal press fitting so that an end portion 1a is formed. Further, the electric wire-connecting portion 1 is subjected to bonding treatment (not shown) in which an adhesive is penetrated into or is applied onto the electric wire-connecting portion 1 so as to secure its waterproofing property.
The electric wire-connecting portion 1 is covered by a heat shrinkable tube 3. One end of the heat shrinkable tube 3 is sealed with a hot melt adhesive 2. Further, the heat shrinkable tube 3 is filled with sealing compound such as butyl rubber.
The electric wire-connecting portion 1 thus covered with the heat shrinkable tube 3 is inserted into a tube shrinking machine 5 in a direction of an arrow as shown in FIG. 10.
A space 5a is formed in the body of the tube shrinking machine 5. As shown in FIG. 10, the space 5a extends in a slit-like manner over from a front end 5b of the tube shrinking machine 5 to one side 5c of the tube shrinking machine 5. The electric wire-connecting portion 1 covered with the heat shrinkable tube 3 is passed through the space 5a of the tube shrinking machine 5. A wire transporting section 6 includes a pair of an upper transport belt 6a and a lower transport belt 6b, which are disposed in the space 5a at the upper and lower portions adjacent to the one side 5c. The transport belts 6a and 6b transport a bundled portion of the electric wires W while holding it therebetween. The wire transporting section 6 is driven by a motor (not shown).
FIG. 11 is a cross sectional view taken along a line XIxe2x80x94XI in FIG. 10. As shown in FIG. 11, a pair of heaters 7 are disposed inside of the tube shrinking machine 5 to sandwich the space 5a. The heaters 7 are used for heating the heat shrinkable tube 3 so as to shrink. The electric wire-connecting portion 1 with the heat shrinkable tube 3 is inserted into the tube shrinking machine 5, and is transported by the transport belts 6a and 6b while the bundled portion of the electric wires W is held therebetween. During the transportation, the heat shrinkable tube 3 is heated by the heaters 7. In accordance with the heating, the heat shrinkable tube 3 shrinks to hermetically seal the electric wire-connecting portion 1 as shown in FIG. 9. As a result, electrical insulation and waterproofing property of the electric wire-connecting portion 1 are ensured, and the electric wire-connecting portion 1 is taken out of the tube shrinking machine 5.
In the above tube shrinking machine 5, however, when the electric wire-connecting portion 1 is transported while the bundled portion of the electric wires W is held between the transport belts 6a and 6b, the electric wire-connecting portion 1 may vibrate in the arrow directions as shown in FIG. 11. As a result, there is a possibility in that the heat shrinkable tube 3 is disengaged from the electric wire-connecting portion 1.
Further, there is a possibility in that the heat shrinkable tube 3 is brought into contact with the heater 7, and therefore it burns.
Furthermore, when the heat shrinkable tube 3 vibrates and the end of the heat shrinkable tube 3 sealed with the hot melt adhesive 2 is too close to the heaters 7, the hot melt adhesive 2 melts and flows out of the end of the tube as shown in FIG. 12. The result is to destroy the structure for securing the electric insulation and the waterproofing property of the electric wire-connecting portion 1.
A first object of the present invention is to solve the above-described possibility. Further, a second object of the present invention is to provide a method of sealing an electric wire-connecting portion to secure electric insulation and waterproofing property thereof. Furthermore, a third object of the present invention is to provide a tube holding tool which perfectly prevents the heat shrinkable tube from vibrating, slipping off, and the hot melt adhesive from flowing out during heat treatment of the heat shrinkable tube. Furthermore, a fourth object of the present invention is to provide a tube shrinking machine for subjecting a heat shrinkable tube covering the electric wire-connecting portion to the heat treatment in the sealing method and by using the tube holding tool.
To achieve the above objects, according the first aspect of the present invention, there is provided a method of sealing an electric wire-connecting portion, comprising steps of: providing a plurality of electric wires, a heat shrinkable tube, hot melt adhesive, and a tube holding tool for protecting one end of the heat shrinkable tube against heat; forming an electric wire-connecting portion by connecting together conductive ends of the electric wires; sealing the one end of the heat shrinkable tube with the hot melt adhesive; attaching the heat shrinkable tube onto the electric wire-connecting portion; attaching the tube holding tool to the one end of the heat shrinkable tube; and heating the heat shrinkable tube to shrink it. Thus, the tube holding tool is attached to the one end of the heat shrinkable tube. Accordingly, when the heat shrinkable tube is heated, there is no chance in that the heat shrinkable tube vibrates and slips off the electric wire-connecting portion, and the hot melt adhesive melts to flow out of the one end of the heat shrinkable tube.
Further, the electric wire-connecting portion can easily be hermetically sealed in a simple manner that the electric wire-connecting portion is covered with the heat shrinkable tube, the tube holding tool is attached to the tube, and the tube is heated. The electrically insulation and the waterproofing property of the electric wire-connecting portion are secured.
According to the second aspect of the present invention, the above method of the first aspect may further comprises a step of bundling the conductive ends of the electric wires.
According to the third aspect of the present invention, the above method of the first aspect may further comprises a step of subjecting an end portion of the electric wire-connecting portion to thermal press fitting.
According to the fourth aspect of the present invention, the above method of the first aspect may further comprises a step of applying an adhesive to the electric wire-connecting portion.
According to the fifth aspect of the present invention, the above method of the first aspect may further comprises a step of cooling the heat shrinkable tube so that the hot melt adhesive is solidified.
According to the sixth aspect of the present invention, in the above method of the first aspect, the electric wire-connecting portion is hermetically sealed with the heat shrinkable tube in the heating step.
Further, to achieve the above objects, according the seventh aspect of the present invention, there is provided a tool for holding a heat shrinkable tube of which one end portion is sealed with hot melt adhesive and the other end portion receives an electric wire-connecting portion formed by connecting together conductive ends of electric wires and covers the electric wire-connecting portion, the tool comprising: a holding portion with which the one end portion of the heat shrinkable tube is held; and a shaft portion integrally formed with the holding portion.
One end of the heat shrinkable tube is capped with the holding portion of the tube holding tool. Therefore, the sealed end of the heat shrinkable tube is protected against the heat during the heating process, and hence there is no chance in that the hot melt adhesive flows out of the sealed end of the heat shrinkable tube.
If the holding portion of the tube holding tool is applied to the sealed end of the heat shrinkable tube and the shaft portion thereof is held, the heat shrinkable tube neither vibrates or slips off the sealed end of the heat shrinkable tube.
According to the eighth aspect of the present invention, in the tool of the seventh aspect, the holding portion and the shaft portion are preferably made of a metallic material.
According to the ninth aspect of the present invention, in the tool of the eighth aspect, the metallic material is preferably aluminum.
According to the tenth aspect of the present invention, in the tool of the seventh aspect, the holding portion preferably has a hollow cylindrical shape having a bottom.
Furthermore, to achieve the above objects, according the eleventh aspect of the present invention, there is provided a tube shrinking machine for shrinking a heat shrinkable tube of which one end portion is sealed with hot melt adhesive and held with a tube holding tool and the other end portion receives an electric wire-connecting portion formed by bundling a plurality of electric wires and connecting together conductive ends of the electric wires and covers the electric wire-connecting portion, the tube shrinking machine comprising: a heater section heating the heat shrinkable tube to shrink the heat shrinkable tube; a wire transporting section located outside the heater section, the wire transporting section transporting the bundled portion of the electric wires; and a tool transporting section located outside the heater section, the tool transporting section transporting the tube holding tool.
The tube shrinking machine includes the tool transporting section for transporting the tube holding tool coupled to the sealed end of the heat shrinkable tube. With the tool transporting section, the heat shrinkable tube neither vibrates or slips off the sealed end of the heat shrinkable tube during the transportation of the heat shrinkable tube for its heating by the tube shrinking machine.
According to the twelfth aspect of the present invention, the tube shrinking machine of the eleventh aspect may further comprises a machine body, wherein a space is formed in the machine body, and wherein the wire transporting section and the tool transporting section are arranged in the space.
According to the thirteenth aspect of the present invention, in the tube shrinking machine of the twelfth aspect, the heater section preferably includes heater groups which are disposed to sandwich the space.
According to the fourteenth aspect of the present invention, in the tube shrinking machine of the eleventh aspect, the wire transporting section is preferably arranged substantially in parallel with the tool transporting section.